1. Field of the Invention
The invention relates to a closure for a container for liquids such as beverages, especially carbonated beverages. In particular the invention provides a screw top cap which seals bottles of carbonated liquid such as soft drinks but is well adapted to seal other containers such as glass or PET containers with contents at above or below atmospheric pressure or having gaseous components or requiring a hermetic seal. Depending on the field of application the closure may comprise a hinge.
2. Description of the Art
Various screw top closures for containers made out of a plastic material, such as polyethylene terephthalate or other materials such as glass are known from prior art. The neck of the containers for these closures are in general standardized and comprise a nearly cylindrical neck portion with an external thread on an outer peripheral surface. An upper end part of the neck portion, positioned above the external thread, has an annular top surface extending substantially horizontally when the bottle is standing upright. A cylindrical outer peripheral surface and a cylindrical inner peripheral surface are extending substantially vertically from the annular top portion. Although many screw tops include a separate sealing gasket within the cap, there is substantial advantage to be had in producing a one-piece cap which avoids the separate sealing gasket.
A one piece cap is shown in the British patent GB788148 (1957), Maxwell, which includes a continuous lip within the top portion of the cap positioned to engage against the annular end face of the opening of the neck of the container and provide a seal between the lip and the free end edge of the neck of the container with the lip curling over at its free edge. However, this cap provides a seal only against the free end edge of the container.
Australian patent application AU15456/76 (1976), Obrist et al., discloses a one-piece cap in which an annular lip extends from the inside top of the cap and engages the inner bore of a container opening so as to curl the free end of the lip in against the bore or inside surface of the opening. However, with this cap, effective sealing requires the inside bore of the opening to be of accurate and consistent dimensions. Furthermore, if carbonated or other gaseous liquid is to be contained, gas pressure will tend to distort the lip and cause a seal failure.
Australian patent application AU14180/83 (1983), Aichinger, describes a cap with two internal sealing structures. One of the structures is an annular shaped outer portion shaped to accept the outer peripheral edge of the free end of the container relying upon the pressure generated during the closing of the cap to seal against this outer edge. Further provided is an inner cylindrical lip to engage the inner bore of the container opening.
U.S. Pat. No. 6,695,161 (2001), Kano et al., is directed to a closure for liquids, especially carbonated beverages, with a seal which shall avoid leaking of the closure because of deformation (doming) due to high internal pressure. However, one draw back of this closure is that it works only in connection with bottles having a special neck portion differing from the above described standardized neck of containers, i.e. wherein the annular top surface and the cylindrical outer peripheral surface of the neck portion must be connected together via an annular boundary surface extending substantially arcuately over a considerable length in a sectional view. Therefore this closure is not suitable for standardized bottles as they are in extensive use on different markets. The seal of the closure described in US'161 comprises an annular seal piece, an annular contact piece and an annular positioning piece which are formed in an outer peripheral edge portion of the inner surface of the top panel wall of the closure. The annular seal piece extends downwardly obliquely in a radially inward direction from the inner surface of the top panel wall and has an outer peripheral surface extending downwardly in a radially inward direction at an inclination angle of about 20°. The annular contact piece is situated immediately inwardly of the annular seal piece and is bulging downwardly in a convex form from the inner surface of the top panel wall. The annular positioning piece is located radially inward arranged at a distance from the contact piece and extends downward substantially vertically from the inner surface of the top panel wall.
U.S. Pat. No. 5,423,444 (1995), Druitt, is directed to a one-piece plastic closure for a container having an externally screw threaded neck as described above. The closure comprises a top portion and an internally threaded skirt and an annular bent sealing rib which projects downwardly from the inside of the top portion. The sealing rib includes a first substantially cylindrical portion contiguous with the top and lying adjacent to or abutting with the skirt and a second, frusto-conical portion contiguous with the end of the first portion distal to the top and extending radially inwardly to terminate in a circular free edge. During threaded engagement of the closure with the neck, the second, frusto-conical portion is engaged by a free end of the neck and folded back against the first, substantially cylindrical portion of the rib to form a gas-tight seal between the neck of the container and the closure.
EP0076778 (1982), Blaser et al., discloses a closure with a circular sealing lip which is arranged in the region of the edge between the outer skirt of the closure and the circular top wall and points obliquely inwards. The sealing lip is made such that it interacts with the outer surface of the neck of the container. At its smallest diameter the sealing lip has a rounded sealing portion and below the sealing portion the sealing lip is widened outwards in the manner of a funnel to receive a container opening. While receiving a container neck the sealing lip rotates about a fulcrum which is located at the base of the sealing lip. The thickness of the sealing lip is in general constant over it's entire length. Due to the oblique arrangement and the thickness of the sealing lip significant resistance has to be overcome while applying the closure to the neck of a container.
EP0093690/U.S. Pat. No. 4,489,845 (1982), Alchinger et al., is directed to a screw-cap with a sealing lip which is affixed to the cap top. The inner side-wall of the sealing lip has a diameter which is greater than the outer diameter of the container opening. The closure further comprises a skirt like clamping device which reaches into the opening of the container neck when the closure is arranged on the neck of the container. This clamping device may itself be designed as an inner seal. According to the description this clamping device creates a contraction of the cap top when the closure is screwed on the neck of a container such that the sealing lip, which is arranged on the outside, is pressed against the container mouth. One problem of this closure is that the described contraction of the whole closure does not significantly occur as described and that the seal is susceptible to imprecision of the neck of the container. A further problem is that this closure needs high torque to proper seal.
U.S. Pat. No. 4,907,709 (1990), Abe et al., describes a combination of a bottle and a closure. The closure has a top wall and a side wall with a thread on the inner surface corresponding to a thread on the outer surface of the neck of the bottle. The closure has an annular shoulder on the inner surface of the top wall thereof which is engageable with the upper surface of the bottle neck and with the outer surface of the bottle neck. An annular rib protruded downward from the top wall of the closure at a place inside of the shoulder to be resiliently engageable with the inner surface of the side wall of the bottle neck. The outer seal of this closure is designed very short and bulky. Due to that it does not provide sufficient flexibility which is necessary to adjust lateral distortion of the neck of the bottle.
All above described closures are injection/compression moulded. With this type of products the sale's price is directly related to the amount of material necessary per closure and the cycle time for injection moulding. Therefore it is advantageous when a closure needs less material and can be produced at lower cycle time such that more closures may be produced.
A problem with the closures known from prior art is that they often fail while being applied to a container by a capping machine at high speed. It often happens that the seal, the thread or the tamper evidence means take damage due to tilted application of the closure on the neck of the container. A further problem is that the closure is ruptured due to external forces. Therefore a good closure should not only use less material and must be produced at high speed it furthermore should also have sufficient mechanical strength to withstand large external handling forces. A good closure further comprises centering means which avoid tilted application of the closure on the neck.
A further problem closures from prior art often suffer is that at high internal pressure of the container the seal fails and content leaks due to doming or lift-off of the top portion of the cap. Especially with caps which seal primarily on the inner peripheral surface or on the annular top surface of the neck of the container this problem may occur.
A still further problem often occurring with closures known from prior art is leakage of the seal due to high internal pressure in the container and additional top load applied to the top of the closure, e.g. due to stacking of several containers. The reason for this can be found in deformation of the closure and therewith related displacement of the seal.
It is an object of the present invention to provide an improved closure suitable for carbonated beverages and other hot or cold liquids, to offer advantages in production such as low cycle time and less material consumption and to be still pressure tight at high internal pressures and top load.